How to link philosophy and physics

Despite knowing very little about it, the evidence for the existence of dark matter is sufficiently strong that it’s explicitly named our standard cosmological model: Lambda Cold Dark Matter. I will present the observational evidence for its existence and provide some examples of the ultra-sensitive observations being pursued to improve our limited understanding of it.

In this talk, I detail collaborative work between astrophysicists and philosophers attempting to search for some of the universe’s “missing” dark matter. Our research group’s hypothesis that some of it resides in dark galaxies—pure dark matter halos that either never possessed or have lost their baryonic matter. We argue that we can locate dark galaxies by their signatures: the gravitational effects that they have on luminous galaxies through collision. But how do astrophysicists blend observation, simulation, and theory to warrant inferences about objects that are not visible at any observable frequency, nor experimentally accessible? In this talk, I focus on a set of philosophical questions connected with an overarching theme of empirical justification and epistemic warrant: Based on our observations, what warrants our belief that we have seen a dark galaxy? Under what conditions should indirect observation be as convincing as direct observation or experiment? What is the structure and justification of such an argument? In attempt to answer these questions, I focus more narrowly on the nature of the astrophysical evidence and the roles that computer simulations play in astrophysical inferences. A deeper understanding of simulations, I argue, is central to providing answers because they connect a vast array of independent astronomical observations/phenomena (each of which are currently best explained by the presence of dark matter) to cosmologists’ more global arguments for dark matter.